Ideal Weight Calculator
See your ideal weight from three established medical formulas — Devine, Robinson, and Hamwi — plus your healthy weight range based on BMI 18.5–24.9.
This calculator provides general estimates for informational purposes only. It is not a substitute for professional medical advice, diagnosis, or treatment. Always consult a qualified healthcare provider.
How It Works
Ideal Body Weight (IBW) formulas were originally developed for clinical use — primarily to calculate drug dosages and assess nutritional status — not as fitness goals. They provide simple height-based estimates of a "reference" body weight.
All three formulas use height in inches above 5 feet (60 inches):
Devine Formula (1974):
Male: IBW = 50 kg + 2.3 kg per inch over 5 ft
Female: IBW = 45.5 kg + 2.3 kg per inch over 5 ft
Robinson Formula (1983):
Male: IBW = 52 kg + 1.9 kg per inch over 5 ft
Female: IBW = 49 kg + 1.7 kg per inch over 5 ft
Hamwi Formula (1964):
Male: IBW = 48 kg + 2.7 kg per inch over 5 ft
Female: IBW = 45.4 kg + 2.3 kg per inch over 5 ft
The differences reflect the eras and populations in which they were developed. The Devine formula is most commonly used in pharmacology. The Robinson formula is slightly more conservative. The Hamwi formula (also called the rule of thumb formula) is widely used in clinical nutrition.
BMI-based healthy weight range:
The World Health Organization defines a healthy BMI as 18.5–24.9. For any given height:
Lower bound (kg) = 18.5 × height(m)²
Upper bound (kg) = 24.9 × height(m)²
This range is generally broader than any single IBW formula and is considered more physiologically realistic for the full adult population.
Frequently Asked Questions
Which formula should I use?
No single formula is definitively best. The three formulas give similar results for people of average height but diverge more for very tall or very short individuals. The BMI-based healthy weight range is arguably the most meaningful for general health purposes, while the Devine formula is the most commonly cited in clinical settings.
Are these formulas accurate for athletes?
No. Like BMI, these formulas do not distinguish muscle from fat. A muscular athlete may weigh significantly more than their calculated IBW while being in excellent health. For athletes, body fat percentage is a more meaningful metric than ideal body weight.
What if I am under 5 feet tall?
The original formulas were validated for people 5 feet and taller. For shorter statures, the formulas technically produce values below the base weight (50, 52, or 48 kg for men). In practice, the BMI-based healthy weight range remains valid for all adult heights.
Should I aim for my IBW?
IBW formulas are reference tools, not prescriptive targets. A healthy weight for you depends on your muscle mass, bone structure, age, and overall health markers (blood pressure, cholesterol, blood sugar). Consult a healthcare provider for personalised guidance.